1. Field of the Invention
The present invention relates to a display apparatus for a television which has a screen with an aspect ratio different from that of original images.
2. Description of the Related Art
In televisions for the NTSC system, the aspect ratio is generally 4:3 (1.333:1). Images to be displayed on a display apparatus include a so-called vista size which accommodates an image having a width larger than that of normal images. The image of the vista size has an aspect ratio of approximately 16:8.6 (1.860:1). In the vista size image, video signals corresponding to portions above and below the image merely represent a black level, while the deflection operation of the television is performed to scan the vista size image in a manner similar to normal images.
Conventionally, for displaying a wider image as mentioned above on a display screen with the aspect ratio of 4:3, the width of the image is made coincident with the width of the screen, and spaces above and below the image is filled with black or gray color. Alternatively, the height of the image is made coincident with the height of the screen, and left and right side portions of the image are cut away.
However, with the first approach, the display screen is not effectively utilized. Moreover, if the display apparatus is used for a long time in such a condition, the difference in deterioration of fluorescent materials and display elements in the black or gray spaces and the image portion possibly causes color phase irregularity or the like.
On the other hand, the second approach presents a problem that video information is partly missing. If the image is scaled down by a constant ratio so as to make the width of the image coincident with the width of the screen, no video information will be missed. However, with this approach, the vista size image is contracted by approximately 28 percents in the horizontal direction, wherein a distorted image can be clearly viewed.
Generally, conventional display apparatuses have been designed in conformity with basic concepts of realizing high fidelity of displayed images, that is, eliminating any missing portion from original images; providing the same aspect ratio; and maintaining the linearity over the whole display screen. Thus, there have been no design thoughts or adjusting methods which dare to damage these concepts.